9 months is not the end of the world. Sometimes bitches have false pregnancies, some matings don't take, you are dealing with nature, it isn't an exact science.
Breeding back to back is fine so long as it is not continuous. EVERY time a bitch is bred she should only be bred if she is in tip-top shape. So if she did not come back well from her previous litter, no, she should not be bred.
Dogs are not humans. A human becoming pregnant twice in two years means 18 months of pregnancy out of 24 -- that is a lot. A dog being bred twice in 1 year, is 4 months of pregnancy out of 12. A human raising a baby means nursing/bottles and diapers for more than 12 months, taking care of the child for 18 years. A bitch takes care of her pups for 8 weeks or less. It is apples to oranges, and so long as the bitch is in good condition it does not hurt them to be bred back to back.
There are other reasons why good breeders might choose to breed just once a year. Managing litters in the summer may be easier in the winter, selling puppies in the spring/summer or fall might be easier than when there is snow and ice everywhere. Some prefer to rest the bitch and breed just once a year. Some might want to breed a different bitch and do not want more than they can handle of puppies.
Nothing is absolute, but a good restaurant generally has a lot of cars in the parking lot, and you might have an hour or more wait for a table. The fact that they have a lot of deposits out there may mean that their dogs are in high demand. That may mean that the dogs used for breeding are good quality and the breeders are well-known. Or not.
I don't like taking deposits until puppies are on the ground. Other breeders want so many deposits before breeding their bitch. It is just different philosophies. If the deposit is non-refundable, than that is what it is. I think if you post a poll on here, how long did you wait for your puppy once you chose a breeder, I would be very much surprised if you have no one saying that they waited 9 months or more.
I also think that that is a lot of possible breedings in 9 months. 6? is that right? That can be a lot, but nothing is cast in stone. If they pass all of your other tests for what kind of breeder they are, then the number of dogs, number of litters would not dissuade me within reason.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC